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Usage Patterns of Minimally Invasive Glaucoma Surgery Differ by Glaucoma Type

Key findings

  • This epidemiologic study compared patterns of standard glaucoma surgery (trabeculectomy or drainage device) to minimally invasive glaucoma surgery (MIGS) in the U.S. between 2013 and 2018
  • 232,537 procedures were reported to the IRIS Registry during that period (203,146 eyes of 160,420 patients). Surgery was most commonly performed for eyes with open-angle glaucoma (78% of all procedures; P<0.001)
  • Eyes with open-angle or normal-tension glaucoma were most likely to receive iStent or Cypass. Those with primary angle-closure glaucoma or secondary glaucoma were most likely to receive standard surgery
  • Of the 21,113 eyes that received multiple procedures, those with open-angle or normal-tension glaucoma were most likely to receive concurrent procedures; endocyclophotocoagulation with iStent was the most common combination
  • Only 9.7% of eyes underwent a MIGS procedure after an initial standard surgical procedure, most commonly endocyclophotocoagulation for eyes with primary angle-closure glaucoma or secondary glaucoma

Uptake of minimally invasive glaucoma surgery (MIGS) techniques has increased in the U.S. over the past decade.

Researchers at Mass Eye and Ear, led by Nazlee Zebardast, MD, MSc, director of Glaucoma Imaging in the Department of Ophthalmology, recently examined current usage patterns for treating U.S. ophthalmic patients by reviewing data from a six-year period.

The team writes in Ophthalmic Epidemiology that the specific glaucoma diagnosis influences the choice of glaucoma procedure as well as the choice of combined and subsequent surgeries.


The researchers used data from the IRIS (Intelligent Research in Sight) Registry—the nation's first electronic health record-based comprehensive eye disease and condition registry, which is maintained by the American Academy of Ophthalmology.

Mass Eye and Ear was one of four academic groups selected nationwide to receive unique access to the IRIS® Registry to help answer large-scale questions about ophthalmic disease. The registry now contains data on more than 71 million patients.

The researchers examined data collected on 232,537 standard or MIGS procedures reported to the IRIS Registry, performed on 203,146 eyes of 160,420 patients between January 1, 2013, and December 31, 2018.

Eyes were subcategorized into 11 diagnosis types:

  • Open-angle glaucoma (OAG)
  • Primary angle-closure glaucoma (PACG)
  • Normal-tension glaucoma (NTG)
  • Pigmentary glaucoma
  • Pseudoexfoliation glaucoma
  • Glaucoma secondary to drugs, eye trauma, eye inflammation, or other eye disorders (considered separately)
  • Other specified glaucoma—hypersecretion glaucoma, glaucoma associated with congenital abnormality, glaucoma associated with vascular disorder, glaucoma associated with increased episcleral venous pressure, and glaucoma associated with aqueous misdirection (considered together)
  • Unspecified glaucoma

Standard glaucoma surgery was defined as:

  • Trabeculectomy
  • Glaucoma drainage device with or without graft (GDD)

MIGS was defined as:

  • iStent
  • Cypass
  • Xen Gel stent
  • Endocyclophotocoagulation (ECP)
  • Goniotomy or ab interno trabeculotomy or Trabectome (hereafter called goniotomy)
  • Canaloplasty

Most Common Diagnoses

Eyes diagnosed with OAG were the most likely to undergo any type of intervention (78% overall; P<0.001).

Most MIGS procedures were for OAG (iStent, 88% of eyes; Cypass, 94%; Xen Gel stent, 90%; goniotomy, 84%; canaloplasty, 84%). OAG accounted for smaller proportions of eyes receiving standard surgeries (trabeculectomy, 76%; GDD, 54%; P<0.001 for each MIGS procedure vs. standard surgery).

Most Common Procedures

The iStent was the most commonly performed MIGS technique, performed principally for OAG (44% of eyes) or NTG (44% of eyes) (P<0.001 for each vs. all other diagnoses).

GDD was the most commonly performed procedure for secondary glaucoma or "other" glaucoma.

Most Common Concurrent Procedures

8,086 concurrent procedures were performed in 7,635 eyes. The most common was ECP with iStent.

Concurrent surgeries were most commonly performed for eyes with OAG or NTG (4.7% and 4.5% of all surgeries for those diagnoses, respectively; P<0.001 for each vs. other diagnoses).

Most Common Subsequent Procedures

6,159 eyes required a subsequent procedure after an initial standard intervention. 90.3% of them received a second standard surgery.

Among the 9.7% of eyes that had MIGS after initial standard surgery, ECP was the most common technique used, particularly in eyes with PACG or secondary glaucoma (P<0.001). ECP represented 51% of the subsequent MIGS procedures for PACG and 68% of those for secondary glaucoma.

Looking Ahead

Adoption of MIGS is likely to intensify because of Medicare reimbursement restrictions on traditional surgeries. These findings can inform future studies of which populations are most likely to benefit from MIGS. They are also expected to guide comparative studies of MIGS procedures versus standard surgeries.

of all glaucoma surgeries were performed for open-angle glaucoma

of glaucoma surgeries after a standard initial surgery were also standard surgeries

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Related topics


Ophthalmologists at Massachusetts Eye and Ear/Massachusetts General Hospital have determined that between 2013 and 2018, the number of minimally invasive glaucoma surgeries surpassed the number of conventional glaucoma surgeries, despite limited evidence of long-term safety or effectiveness.


David S. Friedman, MD, PhD, MPH, and colleagues found that van Herick grading of limbal anterior chamber depth may be useful for identifying iridotrabecular contact, but a relatively high false positive rate limits its usefulness for community-based screening for primary angle closure.